configs: k2g_evm: Enable CONFIG_BLK

CONFIG_BLK can be safely enabled as DM_MMC and DM_USB are already enabled.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Tested-by: Vignesh R <vigneshr@ti.com>